Bol. Mus. Para. Emílio Goeldi. Cienc. Nat., Belém, v. 5, n. 2, p. 195-205, maio-ago. 2010 New occurrence of †Mawsoniidae (Sarcopterygii, Actinistia) in the Morro do Chaves Formation, Lower Cretaceous of the Sergipe-Alagoas Basin, Northeastern Brazil Nova ocorrência de †Mawsoniidae (Sarcopterygii, Actinistia) na Formação Morro do Chaves, Cretáceo Inferior da bacia de Sergipe-Alagoas, nordeste do Brasil Valéria GalloI Marise Sardenberg Salgado de CarvalhoII Hugo Ricardo Secioso SantosIII Abstract: The goal of this paper is to describe a new occurrence of †Mawsoniidae in the Morro do Chaves Formation, Sergipe- Alagoas Basin. This stratigraphical unit is represented by an intercalation of coquina and shale beds, deposited in a lacustrine paleoenvironment during the Upper Barremian (Lower Jiquiá local stage). The description is accomplished on the basis of new and more complete material, represented by articulated bones of the palatoquadrate and lower jaw, as well as by gular plate. It was assigned to the genus Mawsonia based on the presence of a stout angular conspicuously ornamented with wrinkles and ridges, as well as palatoquadrate with a single strengthening ridge on its lateral surface. When this new occurrence of Mawsonia was compared with the other genera of Mawsoniidae occurring in Brazil (i.e., Axelrodichthys and Parnaibaia), it was verified that it differs clearly from Axelrodichthys by the inclination of the suspensorium (obliquely oriented in Mawsonia versus vertically oriented in Axelrodichthys). Regarding Parnaibaia, the ornamentation of the angular and gular plate is more delicate in this genus. Keywords: †Mawsoniidae. Sergipe-Alagoas Basin. Lower Cretaceous. Resumo: O objetivo deste estudo é descrever uma nova ocorrência de †Mawsoniidae na Formação Morro do Chaves, bacia de Sergipe-Alagoas. Esta unidade estratigráfica é representada por uma alternância de camadas de coquina e folhelho, depositadas em um paleoambiente lacustre, durante o Barremiano Superior (no andar local Jiquiá Inferior). A descrição foi efetuada com base em material inédito e mais completo, representado por ossos articulados do palatoquadrado e maxila inferior, bem como pela placa gular. Este espécime foi atribuído ao gênero Mawsonia, com base na presença de um robusto angular conspicuamente ornamentado com cristas e rugas, bem como pela presença de uma crista única, fortalecendo a superfície lateral do palatoquadrado. Quando esta nova ocorrência de Mawsonia foi comparada com outros gêneros de Mawsoniidae presentes no Brasil (i.e., Axelrodichthys e Parnaibaia), verificou-se que ela difere claramente de Axelrodichthys pela inclinação do palatoquadrado (obliquamente orientado em Mawsonia versus verticalmente orientado em Axelrodichthys). Com relação a Parnaibaia, a ornamentação do angular e da placa gular neste gênero é mais delicada. Palavras-chave: †Mawsoniidae. Bacia de Sergipe-Alagoas. Cretáceo Inferior. I Universidade do Estado do Rio de Janeiro. Instituto de Biologia. Departamento de Zoologia. Rio de Janeiro, Rio de Janeiro, Brasil ([email protected]). II Universidade Federal do Rio de Janeiro. Instituto de Geociências. Departamento de Geologia. Rio de Janeiro, Rio de Janeiro, Brasil ([email protected]). III Universidade do Estado do Rio de Janeiro. Instituto de Biologia. Departamento de Zoologia. Rio de Janeiro, Rio de Janeiro, Brasil ([email protected]). 195 New occurrence of †Mawsoniidae (Sarcopterygii, Actinistia)... INTRODUCTION Carvalho & Maisey (2008) recognized only M. gigas and Mawsoniidae is a fossil family of actinistians popularly M. tegamensis, based on unequivocal morphological known as coelacanths, being found in continental and evidence, and synonymized the remnants species with marine paleoenvironments. It possesses a temporal range M. gigas. This species possesses an abundant and wide from the Middle Triassic (Ladinian) to the Late Cretaceous record in Brazil, and is represented by an almost complete (Cenomanian), and a geographical distribution in the South specimen, an articulated skull, fins, and several isolated and North Americas, Africa, and Europe (Schultze, 1993; bones from the Recôncavo, Tucano, Almada, Sergipe- Carvalho & Maisey, 2008; Miguel & Gallo, 2009a). The Alagoas, Araripe, Iguatu, Grajaú, Sanfranciscana, and São taxon was proposed by Schultze (1993) and, since then, Luís basins (see Carvalho & Maisey, 2008). Mawsonia is some studies on its phylogeny in a cladistic context were also represented in the Late Jurassic of the Araripe Basin, accomplished. It is considered monophyletic in the most in the Brejo Santo and Missão Velha formations (Brito recent reviews and includes five unquestionable genera et al., 1994; Malabarba & Garcia, 2000). In addition, (Axelrodichthys, Chinlea, Diplurus, Mawsonia, and Parnaibaia), there is an occurrence of Mawsonia in the Late Jurassic besides others with some taxonomical controversy of the Tacuarembó Formation, Uruguay, being the (Alcoveria, Garnbergia, Indocelacanthus, Libys, Lualabaea, and southernmost record of the genus in South America (M. Trachymetopon). From these, only Axelrodichthys, Parnaibaia Soto, pers. comm., 2010). and Mawsonia are recorded in Brazil. Until now, there are only unpublished data of The monotypic genus Axelrodichthys occurs in the mawsoniids from the Morro do Chaves Formation, Lower Cretaceous of the Araripe Basin, being represented Barremian of the Sergipe-Alagoas Basin. Those are by almost complete and articulated specimens (Maisey, represented by an incomplete caudal fin and portions of 1986), as well as by a juvenile specimen (Brito & Martill, fins referred to Mawsonia (Maffizzoni, 1998, and Ph.D. 1999). Also, there is a record of an articulated skull of Dissertation by A. F. Maffizzoni, defended 2000, entitled this genus in the Lower Cretaceous of the Grajaú Basin “Paleoictiofauna da Formação Coqueiro Seco, Aptiano (Carvalho & Maisey, 1999), as well as isolated bones in the Inferior do Estado de Alagoas, Nordeste do Brasil”). The Upper Cretaceous of Africa (Madagascar; Gottfried et al., paleoichthyofauna of this stratigraphic unit is represented, 2004). In addition, Gee (1988) reported a coelacanth skull besides mawsoniids (Mawsonia sp.), by semionotids roof in the Lower Cretaceous of Africa (Niger), believed (Lepidotes alagoensis), elopomorphs, clupeomorphs to be very similar to Axelrodichthys. sensu lato and paraclupeids, gonorynchiforms (Dastilbe The monotypic genus Parnaibaia is restricted to the sp.), salmoniforms, cimolichthyids incertae sedis Late Jurassic of the Grajaú Basin and is represented by (Atolvorator longipectoralis), and enchodontids (Enchodus almost complete and articulated specimens, as well as sp.) (Gallo & Coelho, 2008; Figueiredo, 2009; Gallo by isolated bones, fin-rays, and scales (Yabumoto, 2008). et al., 2009a; Miguel & Gallo, 2009b). Also, tetrapods, Mawsonia is found all along the Cretaceous of the invertebrates, microfossils, and palynomorphous are South America and Africa, which allows the establishment present (Antonioli et al., 2004, 2009; Carmo et al., of stratigraphical correlations between both continents, 2008; Gallo et al., 2009b). as well as biogeographical approaches. Ancient studies The goal of this paper is to describe a new occurrence point out the existence of six species: four in Africa (M. of Mawsoniidae in the Morro do Chaves Formation, on the lavocati, M. libyca, M. tegamensis, and M. ubangiensis) basis of recently collected material, composed by articulated and two in Brazil (M. brasiliensis and M. gigas). However, bones of the palatoquadrate, lower jaw, and gular plate. 196 Bol. Mus. Para. Emílio Goeldi. Cienc. Nat., Belém, v. 5, n. 2, p. 195-205, maio-ago. 2010 Geological SETTING lacustrine environment, under seasonal dry periods The Sergipe-Alagoas Basin is located in the coastal region when extensive areas were exposed. The dark shales of Northeastern Brazil (Figure 1). The northeastern part were formed in an anoxic environment during the of this basin has a limit with the Pernambuco-Paraíba high level water periods, allowing the preservation of Basin represented by the Maragogi Structural High. To the organic matter. The bivalves lived in shallow and the southwestern, the boundary with the Jacuípe Basin oxygenated waters and their shells were reworked by is not so clear (Campos Neto et al., 2007). storms and accumulated in banks and beaches. The sedimentary succession which crops out in Regarding the age of the Morro do Chaves the São Miguel dos Campos Unit is the most significant Formation, Campos Neto et al. (2007) pointed out an exposure of the Morro do Chaves Formation in the Upper Barremian-Lower Aptian age. More recently, basin. For this succession, the geologist Renato R. C. Antonioli et al. (2009), based on the associated occurrences Ramos constructed a detailed stratigraphic, 75 meters of Aequitriradites spinulosus, Transitoripollis crisopolensis, thick column (Figure 2), summarized in Negrão & and Dicheiropollis etruscus, recognized the palynozone Cavalcanti (2009), as follows: Dicheiropollis etruscus in the lower portion of this From base to top, the first 67 m are characterized by stratigraphical unit, which suggests a Lower Jiquiá local coquina beds ranging from decimeter to meter in thickness. stage (Upper Barremian). These beds are generally amalgamated with horizontal stratification and trough cross-bedding. The coquina shells MATERIAL AND METHODS show variable grades of reworking and recrystallization, In January 2009, the authors carried out extensive field